import System from 'fake-module-system';

const system = new System({
  './foo.js': 'bar'  // a file named foo.js with content "bar"
}); 

// alternate method instead of setting up content in the constructor. 
system.content['./foo.js'] = 'bar';

let module = system.load('./foo.js');

// A module is not actually evaled, or ran. It just stores the code and filename
assert(module.code === 'bar');
assert(module.file === './foo.js');

// You can add custom require extensions for testing (the whole point of this module).
// This unrealisticly simple one just adds "quz" at the end of every file.
system.extensions['.js'] = appendQuzTransform(); 
module = system.load('./foo.js');
assert(module.code === 'barquz');


// Provides convenience method for installing a simple transform.
// This is handy for verifying how your extension behaves with earlier or later extensions.
system.installTransform((code, filename) => {
  if (shouldTransform(filename)) {
    return filename + ' foo';
  }
});
myTransformUnderTest.install(system.extensions);